In a large saucepan, combine the spaghetti sauce, tomato paste,mushrooms and oil. Simmer, uncovered, for 20 min. In a bowl,combine the next 9 ingredients. In a greased 13x9x2" baking pan,layer half of noodles and half of cheese mixture. Top with 2 1/2cup zucchini. Layer with 1/3 of the spaghetti sauce and half ofmozzarella. Repeat layers of noodles, cheese mixture and sauce.Top with tomato slices and remaining sauce and mozzarella. Coverand bake at 350 degrees for 35-40 min. Uncover and bake 10 min.longer. Sprinkle with remaining zucchini. Let stand 20 min. Serves8-10